Not asking customers to manage a local python installation is one thing, although I totally understand how excel + python power users would likely be comfortable bringing and maintaining their own python runtime.
http://python-history.blogspot.com/2009/01/microsoft-ships-p...
There are a lot, I mean a lot apps that support scripting languages and don't need you to manage the language's runtime yourself. Blender's UI is entirely in Python. Civilization games have most game logic in Lua.